The goals of this Project are to (1) develop and characterize new fundamental materials, derived from clay minerals and related layered solids, with properties useful for immobilizing and catalytically decomposing toxic organic chemicals, and (2) utilize these materials in the development of effective remediation technologies for Superfund chemicals. We will continue our studies of the sorptive properties of modified clays, and our efforts to develop biomimetic catalysts that effectively decompose organic toxicants under ambient environmental conditions. In parallel to these efforts, we have initiated a new collaborative study aimed at the implementation of a novel and promising in-situ remediation technology. This technology is based on one class of modified clays, namely organo-clays, which emanate from our earlier basic studies under the auspices of this project. We have shown that organo-clays are effective sorbents for common groundwater contaminants. Our concept for in-situ remediation is that negatively charged clays present in subsoils and aquifer materials can be converted to organo- clays via subsurface injections of cationic surfactants. In this fashion we propose to create in-situ sorptive zones that can be placed to intercept advancing contaminant plumes and remove dissolved organic contaminants. This technology offers the advantage of preventing further aquifer contamination (soil and water) downgradient, and of concentrating contaminants in a defined zone that can be managed to enhance remediation either through biodegradation or catalytic decomposition of the immobilized contaminants. The purposed project is organized around four main lines of investigation: (1) the chemistry of soil modification, (2) the mass transfer aspects of in-situ modification, (3) the hydraulic aspects of in-situ modification, and (4) the development of new sorbents and biomimetic clay materials.